The present invention concerns a method of making coated metal substrates for use in electronic applications. More particularly, the present invention concerns a high volume method of making such coated metal substrates that involves the formation of an integral gang of such substrates.
Porcelain enamel metal substrates are well-known in the prior art and are used extensively in electronic applications. Examples of such substrates and methods of making them are disclosed in U.S. Pat. Nos. 5,605,715 and 5,554,965.
In the prior art such metal coated substrates were generally produced by one of two methods. In one method, the coated substrates are produced individually or one at a time. Unfortunately, this can be a very time consuming and costly approach to producing the coated substrates. In another method, a chisel mark is placed in the base metal during metal fabrication to facilitate the separation of the substrate from the carrier gang frame. During the deposition of the porcelain coating on the base metal the chiseled area is also coated. During the breaking out of the substrate from the carrier gang frame a mechanical parting tool is required and the enamel coating produces fractures in the coating creating a friable unstable edge. Unfortunately, this edge is a source of contamination during subsequent processing and during the breaking out step the fracturing enamel can become an undesirable foreign body in the eyes of the worker who is conducting such breakout.
The present invention allows one to manufacture porcelain enamel coated metal substrates in gangs or groups. Each individual substrate can be easily parted or separated from the gang matrix by hand without chipping the glass-like insulative coating. Thus, no special parting tools are required. Production of the substrates in a gang matrix can result in a significant savings in time and improved handling.
In a preferred embodiment the method of the present invention comprises the steps of fabricating from a section of metal a carrier gang comprising a frame, a piece of base metal which later forms a substrate and a connective portion connecting or linking the piece of base metal to the frame. The connective portion includes a notch. A coating of resist or mask material is applied in the immediate proximity of the notch and then a layer of porcelain enamel coating material is applied to the carrier gang. The resist serves to prevent the deposition of the enamel coating material in the proximity of the notch. After coating the carrier gang is fired in order to cure the enamel. The piece of base metal may be further processed, for example, screen printed with thick films or inks. When required, the piece of base metal can be easily removed from the frame by bending and/or twisting. No mechanical parting tool is required to separate the base metal piece from the frame.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.